Phase 4 Complete: Successfully upgraded to Spring Boot 3.5.0 and Java 21

Co-authored-by: yortch <4576246+yortch@users.noreply.github.com>

Author: Copilot

pom.xml

@@ -5,7 +5,7 @@
     <parent>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-parent</artifactId>
-        <version>3.3.5</version>
+        <version>3.5.0</version>
     </parent>
 
 	<groupId>org.springframework.samples</groupId>